In many instances it is desirable or necessary to regularly monitor the concentration of particular constituents in a fluid. A number of systems are available that analyze the constituents of bodily fluids such as blood, urine and saliva. Examples of such systems conveniently monitor the level of particular medically significant fluid constituents, such as, for example, cholesterol, ketones, vitamins, proteins, and various metabolites or blood sugars, such as glucose. Diagnosis and management of patients suffering from diabetes mellitus, a disorder of the pancreas where insufficient production of insulin prevents normal regulation of blood sugar levels, requires carefully monitoring of blood glucose levels on a daily basis. A number of systems that allow individuals to easily monitor their blood glucose are currently available. Such systems include electrochemical biosensors, including those that comprise a glucose sensor that is adapted for insertion into a subcutaneous site within the body for the continuous monitoring of glucose levels in bodily fluid of the subcutaneous site (see for example, U.S. Pat. No. 6,175,752 to Say et al).
A person may obtain the blood sample by withdrawing blood from a blood source in his or her body, such as a vein, using a needle and syringe, for example, or by lancing a portion of his or her skin, using a lancing device, for example, to make blood available external to the skin, to obtain the necessary sample volume for in vitro testing. The person may then apply the fresh blood sample to a test strip, whereupon suitable detection methods, such as calorimetric, electrochemical, or photometric detection methods, for example, may be used to determine the person's actual blood glucose level. The foregoing procedure provides a blood glucose concentration for a particular or discrete point in time, and thus, must be repeated periodically, in order to monitor blood glucose over a longer period.
In addition to the discrete or periodic, in vitro, blood glucose-monitoring systems described above, at least partially implantable, or in vivo, blood glucose-monitoring systems, which are constructed to provide continuous in vivo measurement of an individual's blood glucose concentration, have been described and developed.
Such analyte monitoring devices are constructed to provide for continuous or automatic monitoring of analytes, such as glucose, in the blood stream or interstitial fluid. Such devices include electrochemical sensors, at least a portion of which are operably positioned in a blood vessel or in the subcutaneous tissue of a patient.
While continuous glucose monitoring is desirable, there are several challenges associated with optimizing manufacture protocols to improve yield and uniformity of the sensing layer and/or other layer (e.g., an overlaying membrane) of the biosensors constructed for in vivo use. Accordingly, further development of manufacturing techniques and methods, as well as analyte-monitoring devices, systems, or kits employing the same, is desirable.